Loud-speaker enclosure



April 26, 1966 E. H. METROS LOUD-SPEAKER ENCLOSURE Filed Sept. 14, 1964INVENTOR.

EDWARD H. METROS ATTORNEY Las United States yPatent O 3,247,926LOUD-SPEAKER ENCLOSURE Edward H. Metros, Uniontown, Pa., assignor offortyeight one-hundredths interest to Edwin G. Warman, Uniontown, Pa. l

Filed Sept. 14, 1964, Ser. No. 396,023 Claims. (Cl. 181-431) Thisinvention relates generally to the field of sound tranducer equipment,and more particularly to improvements in enclosure apparatus forloud-speakers of the cone type which are utilized for the reproductionof music, speech or other audio intelligence.

As an overall object, the present invention seeks to provide soundreproducing apparatus of an improved type adapted to give qualityreproduction performance at moderate cost.

It has been found that extremely realistic and pleasing soundreproduction performance can be achieved when a low-cost, small-sizespeaker, for example, a speaker having an eight-inch cone diameter, isenclosed in a speaker enclosure constructed in accordance with theprinciples of the present invention. This is accomplished without theconventional use of additional speakers or tweeters.

Accordingly, it is a further object of the present invention to providea speaker enclosure of improved design for use with conventionalloud-speakers of any size, but particularly adapted for improving theoverall performance which may be obtained from loud-speakers of thesmaller sizes now seldom considered even usable for overall frequencyreproduction in high fidelity systems.

Another object of the present invention is to provide a speakerenclosure of improved design which is relatively inexpensive tomanufacture and therefore bringing within the means of the averagelistener a sound reproducing syste-m having high quality performance.

Still another object of the present invention is to provide a speakerenclosure having a novel internal construction which eliminatessubstantially all of the hum or reverberation normally associated withenclosures of this type.

Still another object of the present invention is to provide an improvedloud-speaker enclosure having a novel internal construction whichincreases considerably the operating etliciency of the loud-speaker itencloses, especially in the low-frequency ranges.

A further object of the present invention is to provide a speakerenclosure having a novel internal configuration which cancels theundesired sound vibrations which are projected rearwardly of thespeaker.

In accordance with the present invention, a casing is provided which isgenerally parallelepipedal in shape which is completely closed with theexception of a speaker opening provided `in the front wall thereof.Within the casing there is provided a plurality of interconnectedchambers defined by partition members of a predetermined constructionwhich cooperate to absorb and thereby cancel the unwanted Isound wavesprojected rearwardly of the speaker cone. The casing of the presentspeaker enclosure is adaptable for construction from materials havinghard walls and for construction in attractive nonsymmetrically shapedcabinets. Furthermore, the casing as well as the partition memberstherewithin may be formed from relatively inexpensive materials wherebythe overall cost of the present speaker enclosure is considerably belowthe cost of conventional speaker and speaker enclosure combinationsachieving a sound reproduction performance comparable to that of thespeaker enclosure of the present invention.

Housed within the present speaker enclosure is one ice low-costcone-type speaker. The particular arrangement of the partition membersprovided within the present casing cooperates to improve thereproduction qualities of the moderate cost speaker to such an extentthat the results are comparable to, if not better than, loud-speakers ofalmost twice the size and several times that cost housed in ordinaryenclosures.

The above and other objects and advantages of the present invention willbecome apparent from the following detailed description by reference tothe accompanying drawings, in which:l Y

FIGURE 1 is an overall isometric view of the speaker enclosure of thepresent invention;

FIG. 2 is a cross-sectional view taken along the line II-II of FIG. 3;

FIG. 3 is a cross-sectional View taken along the line III- III of FIG.2;

FIG. 4 is a cross-sectional view taken along the line IVIV of FIG. 2;and

FIG. 5 is a fragmentary isometric view further illustrating the internalconstruction of the present speaker enclosure.

Referring now to FIG. 1, there is illustrated a speaker enclosure,generally indicated by the numeral 10, which is generallyparallelepipedal and having a front wall 12 and a rear wall 14 (notshown) which are maintained in spaced parallel relation by means of sidewalls 16 and top and bottom walls 18, 20. The front wall 12 is providedwith a centrally poistioned speaker opening 22 within which rests acone-type speaker 24. The speaker enclosure or casing 10 is completelyclosed with the exception of the speaker opening 22. The casing 10 maybe formed from any suitable cabinet-making materials, such as seasonedwood, plywood, and the plastic materials available today.

Within the interior of the casing 10 there is provided a first soundabsorbing partition 26 which divides the interior of the casing 10 intoa rst inner chamber 28 and a peripheral chamber 30 surrounding the firstinner chamber 28. The first sound absorbing partition 26 comprises wallmembers 32 which are connected and provide a continuous partition. Eachofthe Wall members 32 is secured along one edge to the front wall 12 andprojects therefrom parallel with and spaced from the corresponding loneof the side walls 16, the top wall 18 and the bottom wall 20 of thecasing 10. As can best be seen in FIGS. 2, 4 and 5, the rst partition 26terminates at a peripheral edge 34 which is spaced from the rear wall 14so as to define a peripheral passageway 36 providing communicationbetween the peripheral chamber 30 and the first inner chamber 28. Asupport block 38 is interposed between each wall member 32 and thecorresponding casing wall for supporting the rearward end of the wallmembers 32 against sagging.

The wall members 32 preferably comprise a homogeneous wood-liber boardderived from the repulping of No. l grade news stock, to which is addedwaterproofing ingredients. Material of this type is sold under the tradename of Homasote. Each of the wall members 32 has a plurality ofuniformly spaced apertures 40 which increased their sound absorption.

Disposed within the first inner chamber 28 is a second sound absorbingpartition 42 which is secured to and projectsV rearwardly of the frontwall 12. The second sound absorbing partition 42 defines -a second innerchamber 44 within which is housed the speaker 24. The second soundabsorbing partition 42 preferably comprises an elongated semicylindricalshell which extends parallel with the long dimension of the rectangularfront wall 12 and opens toward the front wall 12. Hence, the secondinner chamber is ibounded by the semicylindrical inner surface 48 of theshell 46 and that inner surface portion 50 of the front wall 12extending between the upper and lower edges of the shell 46. The speakeropening 22 is preferably located centrally of the inner surface portion50 thereby also positioning the speaker 24 centrally within the secondinner chamber 44.

The semicylindrical shell 46 is provided with a plurality of radiallydisposed, large diameter apertures 52 and a plurality of radiallydisposed small diameter apertures 54. As can best be seen in FIGS. 3 and4, the apertures provided in the semicyclindrical shell 46 arealternately large and small, this is, first a row of large apertures 52,then a row of small apertures 54 and so on along the length of theelongated semicylindrical shell 46. The semicylindrical shell 46preferably is formed from wood. Alternatively, the semicylindrical shell46 may be formed from concrete. The semicylindrical shell 46 is open atits opposite ends to provide for communication between the first innerchamber 28 and the second inner charnber 44.

The second partition 42 presents a curved face or an infinite number ofnon-parallel surfaces to the rear face of the speaker 24. The rearwardlymoving sound vibrations emanating from the speaker 24 will impinge thesemicylindrical inner surface 4S of the shell 46 and be partiallyabsorbed through the apertures 52, 54 and partially reflected. Thecurvatureof the shell 46 reduces to a considerable degree the amount ofreflected sound pressures impinging directly or obliquely upon the rearface of the speaker cone. As is known, these reflected sound pressuresif permitted to impinge upon the speaker cone would result in a servedip in the output of the speaker at certain frequencies-this phenomenonis commonly known as choking. However, because of the curved innersurface 4S of the shell 46, a major portion of the rearwardly movingsound vibrations are reflected away from the speaker cone or partiallyabsorbed through the apertures 52, 54.

Referring to FIG. 4, once the reflected sound waves have entered thefirst inner chamber 28, they are substantially entirely prevented fromre-entering the second inner chamber 44 to impinge on the cone of thespeaker 24. Furthermore, the reflected sound waves projected into thefirst inner chamber Z3 are rapidly absorbed by means of the second soundabsorbing partition 26. lt should be noted, in FIG. 4, that the rearwall 14 of the casing is not provided with a sound absorbing surfacematerial as is customary. The conventional sound absorbing material isnot required in the present casing 10 since the second partition 42 isinterposed between any sound waves which will reflect from the rear wall14 toward the speaker 24.

The volume of an enclosure housing a typical eightinch speaker should beat least three and one-half cubic feet in order, for example, to preventthe stiffness of the enclosure from raising the loud-speakers resonantfrequency by more than 10%. Hence, certain rangesV of proportions havebeen found critical, if the unexpectedly desirable results of theinvention are to be fully achieved. These ranges of proportions may bedefined as including constructions in which the lateral dimension of thefront wall 12 running generally perpendicular to the shell 46, i.e., theheight of front wall 12 (as viewed in FIG. 1), is between about 50% and60% of the other dimension of such front wall 12 running parallel to theshell 46, i.e., the width of front wall 12 (as viewed in FIG. 1), and inwhich the distance between the front wall 12 and rear wall 14 is betweenabout 55% and 65% of the last-mentioned other dimension of the frontWall 12. It is to be understood at this time that the present speakerenclosure 10 operates equally as well when positioned horizontally andvrests on either of the walls 18, or when the present speaker enclosure1t) is turned so that it rests on either of the side walls 16. Variousvolume relationships exist in the Ipresent speaker enclosure, whereinthe present speaker enclosure is characterized by having a volumerelationship in which the total volume of the casing 10 and the totalvolume of the first inner chamber are in the approximate ratio of :72.The present speaker enclosure 10 is further characterized by-having avolume relationship in which the total volume of the first inner chamberand the total volume of the second inner chamber are in the approximateratio of 100:23. The speaker enclosure 10 is further characterized byhaving an additional volume relationship in which the total volumes ofthe casing 10, the first inner chamber ZS and the second -inner chamber44 are in the approximate ratio of 100:72:l7. The above quoted volumerelationships are further defined by stating that the casing 10 and thefirst partition member 28 are generally parallelepipedal and the secondpartition member 42, defining the second inner chamber 44, comprises anelongated semicylindrical shell.

Certain dimensional relationships characterize the present speakerenclosure 10. For example, the diameter of the speaker enclosed and theheight, width and depth of the casing should ybe in the approximateratio of 100:200:330:190. Further, the diameter of the speaker enclosed,and the length and diameter of the shell 46 should be in the approximateratio of 100: 145:255. Still further, the diameter of the speakerenclosed and the width, height and depth of the first partition 26should be in the approximate ratio of 100:290:165:l85.

As an illustrative example, a speaker enclosure was constructed inaccordance with the above recited dimensional relationships and volumerelationships in which a low-cost cone-type speaker having an eight-inchcone diameter was enclosed. The dimensions of this enclosure which wasfound very satisfactory in operation and capable of attaining themarkedly improved results characterizing the invention were as follows:The casing 10 had a height of 16.125 inches, a width of 26.5 inches anda depth of 15.25 inches; the first partition 26 had a height of 13.125inches, a width of 23.5 inches and a depth (measured from the front wallto the peripheral edge 34) of 14.75 inches; and the second partition 42(the Semicylindrical shell 46) lhad a diameter of 11.5 inches and alength of 20.5 inches. It should be noted that all of the referencedimensions, the proportions thereof, and those mentioned in the claimsthat follow, refer to the inner dimensions of the casing walls 12, 14and 16; the inner dimensions of the lirst partition wall members 32; andthe inner dimensions of the semicylindrical shell 46. The apertures 40in the wall members 32 were formed on twoinch square pattern and wereone-quarter inch in diameter. The apertures 52, 54 in the secondpartition member were one-quarter and one-sixteenth inch in dia-meter,respectively.

Although the invention has been shown in connection with a certainspecific embodiment, it will be readily apparent to those skilled in theart that various changes in form and arrangement of parts may be made tosuit requirements without departing from the spirit and scope of theinvention.

I claim as my invention:

1. In a speaker enclosure for cancelling rearwardly moving soundvibrations, the combination comprising: a casing having a front wall anda rear wall connected by side walls and top and bottom walls; a firstsound absorbing partition projecting rearwardly from said front wall,said first partition dividing the interior of said casing into a firstinner chamber and a peripheral chamber which surrounds said first innerchamber and communicates therewith; and a second partition interposedbetween said front wall and said rear wall, said second partitiondefining a second inner chamber which is open at its opposite ends toprovide communication between said first inner chamber and said secondinner chamber.

2. In a speaker enclosure for cancelling rearwardly moving soundvibrations, the combination comprising: a

casing having a front wall and a rear wall connected by side walls andtop and bottom walls; first sound absorbing partition means projectingrearwardly of said front wall for dividing the interior of said casinginto a iirst inner chamber and a peripheral chamber, said firstpartition means terminating along a peripheral edge which is spaced fromsaid rear wall to provide communication betweeen said first innerchamber and said peripheral chamber; and second partition meansprojecting from said front wall for defining a second inner chamberwithin said first inner chamber, said second partition member comprisingan elongated shell which is open at its opposite ends to providecommunication between said first and second inner chambers.

3. The combination of claim 1 wherein said speaker enclosure ischaracterized by having a dimensional relationship in which the diameterof the speaker enclosed thereby and the height, width and depth of saidcasing are in the approximate ratio of l00:200:330: 190.

4. The combination of claim 1 wherein said second partition membercomprises an elongated semicylindrical shell opening toward and securedlto said front wall.

5. The combination of claim 4 wherein said second partition is formedfrom Wood.

6. The combination of claim 4 wherein said semicylindrical shell has aplurality of apertures therein which are disposed at uniformly spacedpoints and are alternately of large and small diameter.

7. The combination of claim 4 wherein said shell is characterized byhaving a dimensional relationship in which the diameter of the speakerenclosed thereby, and the length and diameter of said shell are in theapproximate ratio of l00:l45:255.

8. The combination of claim 4 wherein said front wall includes a speakeropening adapted to receive a speaker, which is disposed within saidsecond inner chamber and centrally of said second partition member.

9. The combination of claim 1 wherein said iirst partition membercomprises connected side walls each of which is secured along one edgeto said front wall and each projecting therefrom substantially parallelwith and spaced from the corresponding one of the walls of said casing.

10. The combination of claim 9 wherein said first partition member isformed from a homogeneous, wood-ber board.

11. The combination of claim 9 wherein said casing is generallyparallelepipedal and said speaker enclosure is characterized by having avolume relationship in which the total volumes of said casing and saidfirst inner chamber are in the approximate ratio of 100:72.

12. The combination of claim 1 wherein said casing and said firstpartition means are generally parallelepipedal and said second partitionmember is an elongated semicylindrical shell opening toward and securedto said front wall.

13. The combination of claim 12 wherein said speaker enclosure ischaracterized by having a volume relationship in which the total volumesof said casing, said rst inner chamber and said second inner chamber arein the approximate ratio of l00:72:17.

14. In combination with a speaker having a vibratory sound producingmember characterized by the projection of desired sound waves from oneside thereof and the projection of undesired sound waves from'the otherside thereof: a casing having a front wall provided with a speakeropening and a rear Wall which is connected with said front wall by aplurality of connected side walls, said casing being completely closedexcept for said speaker opening; a iirst apertured partition memberprojecting rearwardly from said front wall and terminating at aperipheral edge which is spaced from said rear wall, said firstpartition member dividing the interior of said casing into a iirst innerchamber containing said speaker opening and a peripheral chamber whichsurrounds said inner chamber and communicates therewith at saidperipheral edge; a second apertured partition member projectingrearwardly from -said front wall and residing within said iirst chamber,said second partition member dening a second inner chamber, said secondpartition memberbeing open at its opposite ends to provide communicationbetween said iirst inner chamber .and said second inner chamber; andmeans mounting said speaker within said second inner chamber With the-side of said vibratory sound producing member from which the desiredsound waves are projected facing said speaker opening and the oppositeside thereof disposed inwardly of said second partition member.

15. In combination with a speaker having a vibratory sound producingmember characterized by the projection of desired sound waves from oneside thereof and the projection of undesired sound waves from the otherside thereof: a casing having a front wall provided with a speakeropening and a rear wall connected with said front wall by means of aplurality of connected side walls, said casingbeing completely closedexcept for said speaker opening; a first partition member comprising aplurality of interconnected side walls each of which is secured alongone edge to said front wall and each of which projects rom said frontwall substantially parallel with and spaced from the corresponding oneof the side walls of saidcasing and all of which terminate along aperipheral edge which is spaced from said rear wall, said tirstpartition member dividing said casing into a first inner chamber and aperipheral chamber which surrounds said rst inner chamber andcommunicates therewith at said peripheral edge, said first partitionmember having a plurality of apertures in each of its side wallsproviding sound absorbing characteristics thereof; a second par titionmember comprising an elongated semicyclindrical shell opening toward andsecured to said front wall, said second partition member extendingtransversely of said speaker opening to dene a second inner chamber,said second partition member being open at each of its ends andterminating along an arcuate edge which is spaced from one of the sidewalls of said iirst partition member to provide communication betweensaid rst inner chamber and said second inner chamber, said secondpartition member having a plurality of apertures formed therein whichrenders said second partition member sound absorbing; and means mountingsaid speaker within said secondinner chamber with the side of saidvibratory sound producing member from which the desired sound waves areprojected facing said opening and the opposite side thereof disposedinwardly of said second inner chamber.

References Cited by the Examiner UNITED STATES PATENTS 2,337,213 12/1943Topping 1Sl3l 3,142,353 7/1964 Todisco 181--31 FOREIGN PATENTS 557,8509/l932 Germany.

467,279 6/ 1937 Great Britain. 729,204 5 1955 Great Britain. 903,995 8/1962 Great Britain.

LEO SMILOW, Primary Examiner.

STEPHEN I TOMSKY, Examiner.

1. IN A SPEAKER ENCLOSURE FOR CANCELLING REARWARDLY MOVING SOUNDVIBRATIONS, THE COMBINATION COMPRISING: A CASING HAVING A FRONT WALL ANDA REAR WALL CONNECTED BY SIDE WALLS AND TOP AND BOTTOM WALLS; A FIRSTSOUND ABSORBING PARTITION PROJECTING REARWARDLY FROM SAID FRONT WALL,SAID FIRST PARTITION DIVIDING THE INTERIOR OF SAID CASING INTO A FIRSTINNER CHAMBER AND A PERIPHERAL CHAMBER WHICH SURROUNDS SAID FIRST INNERCHAMBER AND COMMUNICATES THEREWITH; AND A SECOND PARTITION INTERPOSEDBETWEEN SAID FRONT WALL AND SAID REAR WALL, SAID SECOND PARTITIONDEFINING A SECOND INNER CHAMBER WHICH IS OPEN AT ITS OPPOSITE ENDS TOPROVIDE COMMUNICATION BETWEEN SAID FIRST INNER CHAMBER AND SAID SECONDINNER CHAMBER.